package com.lazar.ke.encrypt;

import org.apache.commons.codec.binary.Hex;
import org.apache.commons.lang3.StringUtils;

import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.math.BigInteger;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;

public class PBKDF2Util {

    public static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA1";


    public static final int SALT_BYTE_SIZE = 32 / 2;         //盐的长度
    public static final int HASH_BIT_SIZE = 128 * 4;         //生成密文的长度
    public static final int PBKDF2_ITERATIONS = 1000;        //迭代次数



    /**
     * 对输入的密码进行验证
     * @param attemptedPassword    待验证密码
     * @param encryptedPassword    密文
     * @param salt                 盐值
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static boolean authenticate(String attemptedPassword, String encryptedPassword, String salt)
    {

        if (StringUtils.isEmpty(attemptedPassword) || StringUtils.isEmpty(encryptedPassword) || StringUtils.isEmpty(salt))return false;
        // 用相同的盐值对用户输入的密码进行加密
        String encryptedAttemptedPassword = encrypt(attemptedPassword, salt);
        if (StringUtils.isEmpty(encryptedAttemptedPassword))return false;
        // 把加密后的密文和原密文进行比较，相同则验证成功，否则失败
        return encryptedAttemptedPassword.equals(encryptedPassword);
    }



    /**
     * 生成密文
     * @param password 明文密码
     * @param salt     盐值
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static String encrypt(String password, String salt){

        if (StringUtils.isEmpty(password) || StringUtils.isEmpty(salt))return "";

        try {
            String key=Hex.encodeHexString(salt.getBytes());
            KeySpec spec = new PBEKeySpec(password.toCharArray(), fromHex(key), PBKDF2_ITERATIONS, HASH_BIT_SIZE);
            SecretKeyFactory f = SecretKeyFactory.getInstance(PBKDF2_ALGORITHM);
            return toHex(f.generateSecret(spec).getEncoded());
        }catch (Exception ex){
            ex.printStackTrace();
            return "";
        }

    }


    /**
     *  通过加密的强随机数生成盐(最后转换为16进制)
     * @return
     * @throws NoSuchAlgorithmException
     */
    public static String generateSalt() throws NoSuchAlgorithmException {
        SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
        byte[] salt = new byte[SALT_BYTE_SIZE];
        random.nextBytes(salt);

        return toHex(salt);
    }


    /**
     *  十六进制字符串转二进制字符串
     * @param hex
     * @return
     */
    private static byte[] fromHex(String hex) {
        byte[] binary = new byte[hex.length() / 2];
        for (int i = 0; i < binary.length; i++) {
            binary[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
        }
        return binary;
    }

    /**
     * 二进制字符串转十六进制字符串
     * @param array
     * @return
     */
    private static String toHex(byte[] array) {
        BigInteger bi = new BigInteger(1, array);
        String hex = bi.toString(16);
        int paddingLength = (array.length * 2) - hex.length();
        if (paddingLength > 0)
            return String.format("%0" + paddingLength + "d", 0) + hex;
        else
            return hex;
    }
}
